Out of the flocks of devoted professionals and amateurs who travel the world hoping to catch those rare minutes when the moon comes between the Earth and sun, casting a shadow over our planet, Pasachoff, a professor at Williams College in Massachusetts, may be the most seasoned.

He is a man on a more-than-30-year mission to study the sun's outer atmosphere—the solar corona—normally hidden behind blue sky and visible from the ground only during total eclipses.

Pasachoff, who is also a National Geographic grantee, has traveled to nearly every continent, collaborating with a global network of academics, technicians, and students, to make sure he's in the eclipse's path. (National Geographic owns National Geographic News.)

He uses high-speed and high-resolution cameras to observe and document changes in the corona's shape.

For the August 1 eclipse, Pasachoff finds himself in Siberia. He recently talked to National Geographic News about the upcoming celestial spectacle.

Why did you pick Russia to view this eclipse?

Pasachoff: This eclipse path goes over Novosibirsk, the third most populous city in Russia, so we could get our personnel and equipment here directly.

And the sun is higher in the sky than it is along the path in Mongolia and China, with much better weather forecasts than earlier in the path near the North Pole or northern Siberia.

What do you hope to see, or discover, with this eclipse?

Pasachoff: We have a series of scientific experiments. The main one is to observe the corona at high resolution through special filters that pass only emissions from the corona—gas at millions of degrees [Celsius].

There are several theories of how the corona gets to be so hot, and we intend our observations of high-frequency coronal oscillations to help discriminate among theories.

You'll be in China for next year's July 22 eclipse. What do you hope to see there?

Pasachoff: Each eclipse is different, and if you get only two minutes and 20 seconds (this year) or 5 minutes and 50 seconds (next year) to see something, you surely can use more time.

The sun varies with the sunspot cycle—or, more generally, the solar-activity cycle. We are at an extreme low in the sunspot cycle now, which shows there is a low level of magnetic activity on the sun.

Low magnetic activity leads to a solar corona that extends much farther in the sun's equator than it does at the poles, where polar plumes of gas are more prominent.

You study the formation of solar wind and other solar phenomena. How do these affect our planet?

Pasachoff: A "solar wind" of particles from the sun hits the Earth. The particles (and also x-rays and other forms of electromagnetic radiation that travel from sun to Earth) cause magnetic storms on Earth, auroras at the poles, and sometimes blackouts of radio communications and even of GPS signals.

We want to be able to predict such storms, and prediction involves understanding the basic mechanisms, which is part of what we are trying to do.

How is this research contributing to science?

Pasachoff: Studying the sun is studying a typical star, so everything we learn about the sun applies to billions of other stars.

And the physical laws of the sun even apply on Earth.

I hope one day we will have fusion reactors to supply us energy on Earth, duplicating not only the nuclear processes of the sun's interior but perhaps also duplicating the holding of extremely hot gas in a magnetic field that takes place routinely in the solar corona.

How has the technology you use changed over the years?

Pasachoff: The advances in technology are fantastic. The electronic cameras we have are at least a hundred times more sensitive than film, so an image we take in ten seconds would have taken a thousand seconds or five minutes on film.

We couldn't have made our high-cadence observations on film; it wouldn't have been sensitive enough.

Further, advances in computers allow us to study the data in ways we couldn't manage before.